The invention relates generally to a safety device for a motor vehicle seat. A typical safety device of this type has a seat surface which is typically formed by a seat cushion and on which a person using the corresponding motor vehicle seat can sit, and a movably mounted (displaceable) securing element which is assigned to the seat surface and can be moved by a drive device, which can be activated in a crash situation, out of a starting position so that, together with the seat surface, it opposes the forward displacement of the pelvis of a person sitting on the seat surface in the longitudinal direction of the seat. In this case, the seat surface extends along a longitudinal direction of the seat which, in the state in which the seat is fitted into a motor vehicle, corresponds, for example, essentially to the longitudinal axis of the vehicle (direction of travel of a motor vehicle).
The seat surface forms, on the one hand, a component of the motor vehicle seat to which the safety device is assigned; however, it simultaneously also forms a component of the safety device itself, since it is intended, together with the securing element, to limit the forward displacement of the pelvis of a person sitting on the seat surface. To this end, the securing element is brought closer to the seat surface (of the seat cushion) by means of the drive device, with it being possible, if appropriate, also for a certain deformation of the seat surface to occur. However, the spatial position of the seat surface as a whole is not changed in this case (e.g. by pivoting the seat surface).
The interaction of the securing element, which is moved out of its starting position, and the seat surface is intended to prevent a person who is buckled up by means of a seat belt of the corresponding vehicle seat from plunging under the seat belt, specifically the lap belt thereof, in a crash situation-induced forward displacement. This effect is also referred to as “submarining”.
In order to oppose the forward displacement of the pelvis of a person sitting on the seat surface in the longitudinal direction of the seat in a crash situation, a series of specific solutions is known from the prior art. A common feature of all of these solutions is that a securing element in the region of the seat surface of the motor vehicle seat is moved with respect to the seat surface in or shortly before a crash situation so that the securing element and seat surface limit the forward movement of the pelvis of a vehicle occupant in the longitudinal direction of the seat or only permit it within a controlled region.
A motor vehicle seat of this type is disclosed, for example, in DE 100 11 819 A1 (incorporated by reference herein). The securing element there is moved in the direction of the seat surface of the motor vehicle seat by means of a pyrotechnic drive in a crash situation.
Not all collisions of motor vehicles in road traffic totally write off the vehicle. There therefore exist a multiplicity of traffic accidents with a collision, in the course of which the movement of the securing element out of the starting position is activated and the vehicle is damaged to a degree making repair of the damage which has occurred to the vehicle to still be worthwhile. Furthermore, it is conceivable for an imminent but ultimately averted collision to be detected by a pre-crash sensor present in the vehicle and for the movement of the securing element out of the starting position to be activated. In such cases, the motor vehicle seat known from the abovementioned publication has the disadvantage that, in particular, the pyrotechnic drive device of the securing element of the motor vehicle seat has to be replaced when the vehicle is being repaired. This results in additional repair costs.